The San Francisco Chronicle posted old photos of snow from 1882, 1951, 1964 and other rare instances of city snowfall – including one photo from the 1976 storm that shows gleeful school kids throwing snowballs.

On Friday, the storm prompted San Francisco Mayor Ed Lee to take precautionary measures. He urged residents to watch out for icy road conditions, and, if possible, avoid driving during the storm’s peak. The city’s public works department was planning to offer free sandbags and emergency crews were on stand-by.

For snow to fall and accumulate in San Francisco, temperatures must drop to 36 degrees, precipitation must be falling and the ground must be chilled for several days beforehand, said Steve Anderson, also a National Weather Service forecaster.

Though it rarely gets that cold in San Francisco, where the surrounding bay and Pacific Ocean generally keeps temperatures moderate, temperatures in San Francisco were expected to drop into the 30s overnight, according to the National Weather Service.